This invention concerns the field of ignition systems for pyrotechnic compositions, and in particular for delayed action pyrotechnic compositions.
These compositions are generally ignited by means of a so-called hot composition (such as a mixture of titanium and boron), itself initiated by a composition sensitive to percussion or to the heating of an electrical conductor.
The compositions are enclosed in a housing whose function is to isolate them from the ambient humidity that deteriorates their properties.
Thus, for initiation by percussion, the housing is closed by a metal sheet (foil) (usually of aluminum or tin) which is sufficiently thin to be perforated by a striker (see for example U.S. Pat. No. 4,841,856).
In order to install such a delayed action system in a non-electrical detonator for a projectile or military explosive charge, it is indispensable to position the ignition system opposite a striker, so that the position at the end of the delayed action period is opposite the pyrotechnic chain to be actuated.
The form of the delayed action component thus depends on the final structure of the detonator, which implies that any change in the design of the system entails the redesign of the delayed action component.
For detonators for rocket projectiles, provision has already been made to separate the percussion detector from a receiving pyrotechnic composition by a pipe. Refer in particular to U.S. Pat. No. 2,730,046 and French Patent No. 2533687.
However, the receiving composition is always another detonator which is initiated by the impact resulting from the projection of metallic fragments, this impact being perfectly capable of initiating the detonation through the foil.
In fact, the hot compositions required to ignite delayed action pyrotechnic compositions are not sufficiently sensitive to impact to be able to be initiated directly in this way, and it is therefore necessary to provide an additional detonator upstream from the hot composition, a detonator that is initiated directly by a striking pin (with the problems of definition of the geometry of the delayed action discussed above), or by means of a pipe.
In all cases, the impact sensitivity of the ignition system is enhanced. If a pipe is used, it must be rectilinear to avoid decreasing the energy of the projected particles.
The object of the invention is to overcome these drawbacks by proposing an ignition system that is insensitive to impact, and which can be initiated remotely by means of an igniter.